Image transfer mechanism



M 7, 1970 D, MCNMR Em 3,519,343

IMAGE TRANSFER MECHANISM Filed July 1, 1968 nmliwmm lsx FIG.4

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DAVID D MCNAIR ROYCE D. PICKERING AfiNZiNTORS ATTORNEYS United States Patent 3,519,343 IMAGE TRANSFER MECHANISM David D. McNair and Royce D. Pickering, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed July 1, 1968, Ser. No. 741,388 Int. Cl. G03g 15/00 U.S. Cl. 355-4 5 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION An apparatus of this invention may be utilized in the device disclosed in commonly assigned U.S. patent application, Ser. No. 741,359, filed July 1, 1968', entitled Printing Apparatus to John S. Pollock.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a transfer device for the transfer of electrostatic toner images from the surface of a photoconductive component to a receiving surface, and more particularly to such a device for transferring images from a plurality of photoconductive components onto a single receiving surface in registry.

Description of the prior art The problem of registering electrostatic toner images has been largely ignored because in most instances only one image was transferred to each receiver. Mostattempts to superimpose a plurality of toner images involve trying to precisely align optical systems for three color separation images with the position of exposure stations and separate transfer stations to provide exact optical alignment of electrostatic toner images on a receiver to obtain registry. However, as a practical matter, these methods are not very satisfactory because of extreme difficnlty in maintaining all parts in proper alignment at all times. Thus, the need for a convenient way of aligning each photoconductor with the receiver for each transfer of an image is apparent.

This alignment problem is of particular importance in copying color originals. In the usual electrophotographic process, an original, such as a color negative, is broken down into its three color components by the use of beam splitters, filters, etc. as is well known in the art. Colorseparation images thus formed are then projected on to different photoconductive surfaces to form three separate electrostatic images. These images are each toned with a toner having a complementary color to each color separation image. The toned images are finally transferred in registry to a receiver to form a composite color print. Unless the registration of the toner images is held within very narrow limits, the resulting print will be unsatisfactory.

SUMMARY OF THE INVENTION The present invention overcomes this problem by providing a transfer roller to which a receiver is attached.

3,519,343 Patented July 7, 1970 This roller has involute teeth which are adapted to engage a tapered surface of rack teeth formed as registration holes in separate photoconductive chips or chipholders to which a chip is attached to move them into aligned relationship with the receiver on the roller so that subsequent image transfers are made in registry on the receiver. The involute faces of the teeth serve to provide longitudinal alignment whereas lateral alignment is provided by a tapered side surface on one of the teeth which engages a side edge of one of the registration holes. As the involute teeth engage the registration holes in a photoconductive chip, or chipholder, the chip or chipholder is moved away from its registration pins so that the photoconductor is drawn into proper alignment with the receiver. After this occurs and before the involute teeth disengage from the registration holes, the chip or chipholder may be held or locked in position by suitable means, such as an electromagnet, to prevent movement as the roller moves across the chip so that the toner image on the photoconductive surface thereof may be transferred to the receiver in registry.

Additional objects and novel features of this invention will become apparent from the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary longitudinal section showing the transfer mechanism of this invention prior to engagement with a photoconductive chip;

FIG. 2 is a fragmentary longitudinal section, similar to FIG. 1, but showing the mechanism in an engagement with a photoconductive chip;

FIG. 3 is a fragmentary longitudinal section, on an enlarged scale, showing the position of an involute tooth as it first engages a photoconductive chip in solid lines and showing the position of the involute tooth just prior to release of a photoconductive chip in dotted lines; and

FIG. 4 is a longitudinal section taken along lines 4--4 of FIG. 1, showing the relationship between involute teeth and registration holes in a photoconductive chip.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with this invention, a transfer mechanism is provided which includes a transfer roller 10 rotatably mounted on a frame 11 movable along a suitable support, such as rails (not shown). The base is attached to a timing belt 12 which is driven by a motor 13 through an endless belt 14 which serves to move the transfer roller across photoconductive chips 15. Transfer roller 10 can be rotated by a pair of gears 16 and 17 at opposite ends thereof, as best seen in FIG. 4 which engage a pair of racks 18 and 19, respectively. Of course, a single gear and rack may be used, if desired. A receiver in the form of a sheet 21 may be attached to transfer roller 10 in any suitable manner and will be brought into rolling engagement with photoconductor 22 on photoconductive chip 15. The photoconductor has been illustrated as being fixedly attached to a base to form chip 15. However, it may be desirable to have the photoconductor be a separate member or chip which is removably attached to a chipholder, as by a vacuum.

The photoconductive surface has an electrostatic image formed thereon in a conventional manner which is then toned. This toned image is then transferred to a receiver by the means described. As the roller is transported across the surface of the photoconductors by timing belt 12, the rack and gear arrangement assures that the transfer roller 10 is properly oriented with respect to each chip and is rotated at the proper rate to assure accurate registration of the images from each chip.

Each chip is fed from a suitable development station into engagement with registration pins 23 which serve to make a gross alignment of the chips for transfer, where it is supported by suitable rails or guides (not shown). However, the final alignment or registration of the chips is accomplished by involute teeth 24 and 25. As transfer roller moves to the right, it is rotated in a counterclockwise direction by gears 16 and 17 engaging with racks 18 and 19 so that teeth 24 and 25 are brought into engagement with registration holes 26 and 27. These registration holes are actually rack teeth which are engaged by the involute teeth to move the chips into proper position just prior to the receiver coming in contact with the photoconductor. Transfer roller 10 is phased so that there is an initial misregistration of the involute teeth and the registration holes. When the involute surface 28 engages the registration holes, as in FIG. 3, chip 22 is moved quickly so that the teeth and registration holes are in alignment. Then the teeth roll on tapered surface 29 of the registration holes for a short period of time while a locking means, described below is activated. Then transfer roller 10 rolls across photoconductive surface 22 so that the toner image is transferred to receiver 21 on the transfer roller. This movement provides for longitudinal alignment of the chip with the receiver so that just as the involute surface 28 disengages from wall 29, as shown in dotted lines in FIG. 3, the end of receiver 19 is properly aligned with photoconductor 22. Lateral alignment is accomplished by tapered side surface 31 on involute tooth 24, as shown in FIG. 4, which engages a side wall of registration hole 26 and movesthe chip to the left, as viewed in FIG. 4. After the chip has been properly aligned, an electromagnet 32 may be energized by closing a microswitch 33 to hold the chips in fixed position during the transfer operation. The angle of tapered surface 29 is the same as the pressure angle of the involute tooth selected. The greater the angle to the perpendicular the longer the contact time between the involute tooth and tapered Wall 29 of the registration hole. An angle of is satisfactory but other angles could be used. It is only important that this engagement last long enough after movement of the chip for the electromagnet to be energized and lock the chip in place.

Of course, it will be understood that the transfer step is repeated for each chip in the sequence so that the toned image on each chip is transferred to the receiver in registry to form a composite print, such as a color print. Conveniently, chips 22 are spaced from each other so that involute teeth 24 and will engage registration holes 26 and 27, respectively of each chip for alignment. Following transfer, the chips are moved out of the transfer station so that additional chips may be brought into place for the next transfer. The transfer. roller may either be moved back to the position shown in FIG. 1 by reversing the timing belt 12 or by letting the belt continue in the same direction until the transfer roller is brought back to its initial position. It will be understood that additional transfer rollers may also be provided on the timing belt so that another transfer may be made immediately to provide a substantially continuous printing operation.

From the foregoing, it can be seen that the novel features and the advantages of this invention are readily apparent. The involute surface of teeth on a receivercarrying roller pull the photoconductive chip away from the registration pins to provide longitudinal alignment and a beveled surface on one of the teeth moves the chip away from the lateral registration pin to provide lateral alignment. After alignment, an electromagnet locks the chip in place just before the transfer of a toner image from the photoconductor to the receiver.

The invention has been described in considerable detail with reference to a preferred embodiment thereof, it will be understood that variations and modifications can be efiected within the spirit and scope of the invention.

We claim:

1. A mechanism for transferring in registry an electrostatically held toner image from each of a plurality of photoconductive chips, onto a single receiver, each said chip having means defining at least one registration hole therein, said mechanism comprising:

a rotatable transfer means, for carrying said receiver;

at least one involute tooth extending from said transfer means and engageable with a surface of said registration hole defining means in each chip'to sequentially align each said chip with said receiver; and

means for rotatably moving said transfer means past said chips so that said involute tooth sequentially engages said registration hole defining means in both of said chips and said images on said chips are transferred sequentially to said receiver in registry.

2. A mechanism, as claimed in claim 1, wherein said hole defining means includes:

a tapered surface engageable by said involute tooth.

3. A mechanism, as claimed in claim 1, wherein said involute tooth includes:

a beveled side surface for engagement with a side edge of each of said registration hole defining means to laterally align said chips with said receiver.

4. A mechanism, as claimed in claim 1, further including:

an electromagnet adjacent each of said chips energizable after said chips are aligned to hold them during transfer of said images from said chips to said receiver.

5. A mechanism for transferring in registry an electrostatically held toner image from each of a plurality of photoconductive chips onto a single receiver, each said chip having means defining at least one registration hole therein with a tapered surface, said mechanism comprising:

a rotatable transfer roller, for carrying said receiver;

at least one involute tooth extending from said roller and engageable with said tapered surface of said registration holedefining means in each of said chips to longitudinally align said chips with said receiver, said tooth having a beveled side surface for engagement with a side edge of each of said registration hole defining means to laterally align said chips with said receiver;

an electromagnet adjacent each of said chips energizable after said chips are aligned to hold them during transfer of .said'images from said chips to said re ceiver; i

means for moving said transfer roller sequentially past said chips to bring said receiver into rolling engagement therewith; and

means for rotating said transfer roller as said roller is moved'past said chips so that said involute tooth engages said registration hole defining means and said images on said chips are transferred to said receiver sequentially and in registry.

References Cited UNITED STATES PATENTS 3,399,611 9/1968 Lusher 355-4 3,414,353 12/1968 Schwardt 355--18 NORTON ANSHER, Primary Examiner L. H. McCORMICK, JR., Assistant Examiner U.S. c1. X.R. 117-475; 35518 

